The r.f. discharge of sputtering silicon target using argon-oxygen-nitrogen plasma was investigated by optical emission spectroscopy. Electronic temperature (T-e) and emission line intensity were measured for different plasma parameters: pressure (from 0.3 to 0.7 Pa), power density (0.6-5.7 W cm(-2)) and gas composition. At high oxygen concentration in the plasma, both T, and the target self-bias voltage (V-b) steeply decrease. Such behaviour traduces the target poisoning phenomenon. In order to control the deposition process, emission line intensity of different species present in the plasma were compared to the ArI (lambda = 696.54 nm) line intensity and then correlated to the film composition analysed by Rutherford Backscattering Spectroscopy. (c) 2006 Elsevier B.V All rights reserved.